pry-timetravel

Time travel! For your REPL!

> x = 5
5
> snap
> x = 10
10
> back
> x
5

This is an attempt to package the proof of concept. API WILL CHANGE!

How it works

The 'snap' command causes a fork, and the child is sent a SIGSTOP to freeze the process. The parent continues on. Later when you do 'back' the saved child is sent SIGCONT and the current process is sent a SIGSTOP. Ultimately you can have a whole pool of frozen snapshots and can resume any of them.

In theory copy-on-write semantics makes this a tollerable thing to do :)

There are a few more details, but that is the important bit.

WARNING: Time travel may cause zombies.

KNOWN ISSUES

Redis fork detection

Redis checks to see if you forked and yells at you about needing to reconnect. Reasonably so, as it is a crazy idea to use the same connection in forked children! But we are doing crazy things. In 3.1.0 the gem will auto-reconnect, or you can pass inherit_socket to the connection to stop that. Or you can do this to bypass safety measures:

class Redis
  class Client
    def ensure_connected
      yield
    end
  end
end

Maybe this will be a default hack that gets activated on your first snapshot at some point in the near future.

pry-timetravel

How it works

KNOWN ISSUES

Redis fork detection

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